(CN) — Think of a moment when you realized you were dreaming.
Known as lucid dreaming, it can be a strange feeling for a person to knowingly experience the surreality of a dream. It’s also a phenomenon that researchers can use to better understand what happens during REM sleep.
While dreaming, participants in sleep experiments were able to perceive questions from scientists, and answer them, according to research published Thursday in the journal Current Biology.
To conduct the experiments, researchers first had to train 36 people to reach a lucid dream — a process using four different methods at various test sites, all described in the new paper.
In a video released along with the research, scientists explain how it’s possible to make yourself realize you’re dreaming. It’s called a “reality check.”
Study author Karen Konkoly, who is studying for her doctorate at Northwestern University, explained a reality check as the moment “when you ask yourself, very sincerely, am I awake or am I dreaming?”
One trick to getting the answer is to study your hands, Konkoly said in the video. “A lot of times, in dreams, they become really strange.”
Bizarre storylines can be a hint, too. Or if you read something in a dream, look away, then return to looking at the text — “a lot of times, in a dream, the words will change,” Konkoly said.
“The best reality check is just to become really critically aware,” she said, of aspects different from a “normal, waking experience.”
In Konkoly’s team’s experiments, participants were fitted with EEG, or electroencephalography, monitors so researchers could study their brain activity as they dozed.
The EEG sensors showed which stage of sleep a participant is in, as well as where they were looking.
Tracking the eyes was important, because study subjects used eye movements or contracted facial muscles, to communicate with researchers.
Once a study subject was in a lucid dream, researchers asked them yes-or-no questions and simple math problems, and the participants’ nonverbal replies resulted in a dialogue that researchers call “interactive dreaming.”
"We found that individuals in REM sleep can interact with an experimenter and engage in real-time communication," study author Ken Paller, a researcher at Northwestern University, said in remarks released with the study.
"We also showed that dreamers are capable of comprehending questions, engaging in working-memory operations, and producing answers.
The paper demonstrates something that most people would have predicted is impossible, Paller explained, assuming “that people would either wake up when asked a question or fail to answer, and certainly not comprehend a question without misconstruing it."
Some of the study subjects had minimal experience with lucid dreaming before the experiments. Others were frequent lucid dreamers, including a patient with narcolepsy.
It was the more experienced individuals who were able to express more robust responses to the researchers, and showed an ability to maintain information in their working memory while they slept.
“Their responses included distinctive eye movements and selective facial muscle contractions,” the researchers write, and the six individuals correctly answered questions on 29 occasions.
The “repeated observations of interactive dreaming” seen across the four different laboratory groups demonstrate that “phenomenological and cognitive characteristics of dreaming can be interrogated in real time,” which the study authors say can open up new doors for research.
When scientists study dreaming, they typically have to rely on reports from study subjects after they wake up. Anyone who’s tried to describe a dream to someone else knows how fragmented and nonsensical that process can be.
“Retrospective dream reports are subject to distortion and forgetting,” the study authors write, “presenting a fundamental challenge for neuroscientific studies of dreaming.”
The new research, a proof-of-concept study, aims to overcome that research barrier by demonstrating two-way, mid-dream communication, which can be used in future studies of dreams, memory, and how sleep affects memory storage.
“Our experimental goal is akin to finding a way to talk with an astronaut who is on another world,” Thursday’s study says. “[B]ut in this case the world is entirely fabricated on the basis of memories stored in the brain.”
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